Furnaces and similar apparatus include pipes that carry hot gases and/or liquids. These gases or liquids usually carry some proportion of unwanted contaminants that eventually become attached to the insides of the pipes and begin to clog them.
When the pipes are cleaned, access to the pipes is often carried out through a furnace header that is located at the end of two or more pipes. Gas or liquid flow through the two or more pipes is from one and into the other or others. The cleaning of such pipes has previously typically required the insertion of a cable with a cleaning device attached to one end that is moved through the pipes to clean them, rather like a chimney sweep. The cleaning device may use high pressure jets. The cable and cleaning device access the pipes through the furnace header which provides an opening for each pipe. Plugs are used to seal off the furnace headers when they are not being used to clean the pipes.
The inventor has begun cleaning pipes in furnaces and such like using an elastic, cylindrical device with sharp spines, known as a pig. The pig fits snugly within the pipe and is forced through the furnace under fluid pressure. The elasticity of the pig allows it to pass around 180.degree. bends. Commonly used furnace headers have formed an insurmountable barrier for these pigs. The invention has therefore designed a plug for a furnace header that includes a generally concave arcuate surface forming a 90.degree. bend whose edges merge with the internal dimensions of the furnace header to allow the pig to pass from one pipe in the furnace header to the other. Further description of the invention is found in the description following and the claims.